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SAN FRANCISCO, CA - AUGUST 11: A view of the Millennium Tower on August 11, 2016 in San Francisco, California. A $500 million lawsuit has been filed against building owner the owner of the Millennium Tower, Millennium Partners, and the Transbay Joint Powers Authority after it was revealed that the building had sunk 16 inches into the ground and is leaning two inches to the northwest. The 58-story, 419-residence building was completed in 2009. (Photo by Justin Sullivan/Getty Images)

A UC Berkeley structural engineering professor is expected to be the star witness Thursday at the San Francisco Board of Supervisors hearing on the sinking and tilting Millennium Tower building.

“It would appear to anybody that corners were cut,” Supervisor Aaron Peskin said about the troubled 58-story high-rise project, which has sunk 16 inches since it was built.

On Thursday, he said, he wants to press the Berkeley professor who signed off on the now sinking foundation in a letter to the city in early 2006.

That expert, Jack Moehle, refused to voluntarily appear and had to be subpoenaed to City Hall. Moehle declined to comment Wednesday, saying he prefers to wait until his testimony.

In the document, engineer D. Michael Holloway of InSituTech in Orinda, said the test results were generally good, but they also raised questions about the “suitability” of the foundation design.

The plan was to use 900 slender 14-inch square piles. But Holloway noted that the soil layers, or strata, had a “rather complicated” “variability,” and said less was known about the layers on the south side of the project. Such variations could lead to some piles not holding fast in the ground.

“Our findings need to be factored into the design of the overall foundation system,” Holloway concluded in his November 2005 memo.